The use of thin Film Substrates to Study Enhanced Solid-State Phase Transformations

1993 ◽  
Vol 319 ◽  
Author(s):  
PAUL G. Kotula ◽  
Dwight D. Erickson ◽  
C. Barry Carter
Keyword(s):  
Thin Film ◽  
Phase Transformation ◽  
Solid State ◽  
Phase Transformations ◽  
Pulsed Laser ◽  
Alumina Layer ◽  
Transition Alumina ◽  
Transmission Electron ◽  
Film Substrate ◽  
Alpha Alumina

AbstractA thin-film substrate geometry is described for the study of enhanced or seeded solid-state phase transformations. As an example of this approach, thin films of hematite have been used as substrates for the study of the seeded phase transformation of a boehmite-derived transition-alumina to α-A12O3. The hematite films were grown on bulk (0001) α-A12O3 single crystal substrates by pulsed-laser ablation. A layer of a boehmite sol was then spin-coated onto the thin film. The assemblages were then heated to 950°C, or 1000°C in order to induce the phase transformation. Specimens were imaged in cross section by transmission electron microscopy. No transformation was observed for specimens heated to 950°C. In specimens heated to 1000°C, the transition alumina was found to transform to alpha-alumina, starting at the surface of the hematite film, via solid-state heteroepitaxy. In this case, islands, growing out from the hematite film into the transition alumina layer, were observed.

Characterization of metallurgical-grade aluminas and their precursors by 27Al NMR and XRD

2007 ◽  
Vol 85 (10) ◽  
pp. 889-897 ◽  
Author(s):  
Linus M Perander ◽  
Zoran D Zujovic ◽  
Tania Groutso ◽  
Margaret M Hyland ◽  
Mark E Smith ◽  
...  
Keyword(s):  
Solid State ◽  
High Field ◽  
Structural Complexity ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Nmr Studies ◽  
Transition Alumina ◽  
Angle Spinning ◽  
Alpha Alumina

The structure of metallurgical- or smelter-grade aluminas (MGAs) is complex and poorly understood. Ultra-high-field solid-state 27Al NMR results on industrial as well as on laboratory-prepared aluminas are discussed in relation to XRD results. It is demonstrated that high-field NMR can effectively be used to quantify the proportion of the thermodynamically stable alpha-alumina phase in these materials. The results demonstrate that 27Al NMR is a vital adjunct to XRD methods to quantify the transition alumina phases that invariably dominate the MGAs. The nature of the disorder in these materials, determined by 27Al NMR, is also compared with literature data, such as XANES and EXAFS studies, on typical laboratory-prepared materials. The utility of 27Al NMR studies to provide new insight into the structural complexity of metallurgical aluminas is shown.Key words: solid-state magic-angle-spinning NMR, metallurgical-grade alumina, transition alumina, gamma-alumina, coordination number.

Substrate Latent Heat Effects in The Calculations for Pulsed Laser Irradiated Thin Films

1983 ◽  
Vol 13 ◽  
Author(s):  
J.J. Cao ◽  
K. Rose ◽  
O. Aina ◽  
W. Katz ◽  
J. Norton
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Pulsed Laser ◽  
Phase Changes ◽  
Morphological Observation ◽  
Substrate Structure ◽  
Heat Effects ◽  
Film Substrate ◽  
Scanning Electron ◽  
Pulsed Laser Irradiation

ABSTRACTWe present a numerical model for the calculation of the temperature rise caused by pulsed laser irradiation of a thin film/substrate structure. This model includes phase changes in both the thin film and the substrate. The inclusion of phase changes results in more complex thermal behavior and significantly affects melt durations. This model was applied to the AuGe/GaAs system. Morphological observation using the scanning electron microscope and SIMS profiles provides experimental verification for the numerical calculations.

Microstructural Transformations in Alumina Gels

1984 ◽  
Vol 32 ◽  
Author(s):  
F. W. Dynys ◽  
M. Ljungberg ◽  
J. W. Halloran
Keyword(s):  
Phase Transformations ◽  
Microstructural Development ◽  
Transition Alumina ◽  
Hydrous Oxides ◽  
Alumina Gels ◽  
Alpha Alumina

ABSTRACTMicrostructural development in alumina gels is dominated by a series of phase transformations between the hydrous oxides to transition alumina phases, between transition phases, and transformation to alpha-alumina. These microstructural transformations are illustrated in boehmite AlOOH and bayerite Al(OH)3 gels.

In-Situ High Resolution Transmission Electron Microscopy of Dynamic Events During the Amorphous to Crystalline Phase Transformation in Silicon

1985 ◽  
Vol 62 ◽  
Author(s):  
M. A. Parker ◽  
T. W. Sigmon ◽  
R. Sinclair
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Transformation ◽  
Solid State ◽  
High Resolution ◽  
Elevated Temperatures ◽  
Video Recording ◽  
Dynamic Events ◽  
Transmission Electron

ABSTRACTA technique has been developed which employs high resolution transmission electron microscopy (HRTEM) for the observation of the atomic mechanisms associated with solid state phase transformation as they occur at elevated temperatures. It consists of the annealing in-situ of cross-section transmission electron microscopy (TEM) specimens that have been favorably oriented for lattice fringe imaging and the video-recording of dynamic events as they occur in real-time. By means of this technique, we report the first video-recorded lattice images of crystallographic defect motion in silicon, viz. the motion of dislocations and stacking faults, as well as the first such images of the atomic mechanisms responsible for the amorphous to crystalline (a-c) phase transformation, viz. heterogeneous nucleation of crystal nuclei, coalescence of crystal nuclei by co-operative atomic processes, ledge motion at the growth interface, and normal growth in silicon. This technique holds great potential for the elucidation of the atomic mechanisms involved in reaction kinetics in the solid state.

Analysis of Interface Dynamics in Solid-State Phase Transformations by In Situ Hot-Stage High-Resolution Transmission Electron Microscopy

1994 ◽  
Vol 332 ◽  
Author(s):  
James M. Howe ◽  
W. E. Benson ◽  
A. Garg ◽  
Y.-C. Chang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Solid State ◽  
High Resolution ◽  
Phase Transformations ◽  
Interface Motion ◽  
Transmission Electron ◽  
Kinetics Of ◽  
Dynamics Of Interfaces

ABSTRACTIn situ hot-stage high-resolution transmission electron microscopy (HRTEM) provides unique capabilities for quantifying the dynamics of interfaces at the atomic level. Such information is critical for understanding the theory of interfaces and solid-state phase transformations. This paper provides a brief description of particular requirements for performing in situ hot-stage HRTEM, summarizes different types of in situ HRTEM investigations and illustrates the use of this technique to obtain quantitative data on the atomic mechanisms and kinetics of interface motion in precipitation, crystallization and martensitic reactions. Some limitations of in situ hot-stage HRTEM and future prospects of this technique are also discussed.

Acetone and ethanol solid-state gas sensors based on TiO2 nanoparticles thin film deposited by matrix assisted pulsed laser evaporation

2007 ◽  
Vol 127 (2) ◽  
pp. 426-431 ◽  
Author(s):  
R. Rella ◽  
J. Spadavecchia ◽  
M.G. Manera ◽  
S. Capone ◽  
A. Taurino ◽  
...  
Keyword(s):  
Thin Film ◽  
Solid State ◽  
Tio2 Nanoparticles ◽  
Gas Sensors ◽  
Pulsed Laser ◽  
Laser Evaporation

A Mixed-Mode Model Considering Soft Impingement Effects for Solid-State Partitioning Phase Transformations

2011 ◽  
Vol 172-174 ◽  
pp. 561-566 ◽  
Author(s):  
Hao Chen ◽  
Sybrand van der Zwaag
Keyword(s):  
Phase Transformation ◽  
Solid State ◽  
Numerical Solution ◽  
Phase Transformations ◽  
Concentration Gradient ◽  
Mixed Mode ◽  
Original Model ◽  
Polynomial Method ◽  
Soft Impingement ◽  
Kinetics Of

The original mixed-mode model is reformulated by considering the soft impingement effect and applying a general polynomial method of dealing with the concentration gradient in front of the interface. Comparison with the numerical solution shows that the reformulated mixed-mode model is more precise than the original model. The effect of soft impingement on the kinetics of partitioning phase transformation depends on both the growth mode and the degree of super-saturation.

scholarly journals Single-crystal to single-crystal guest exchange and phase transformations in a porous metallocycle

CrystEngComm ◽  
2014 ◽  
Vol 16 (20) ◽  
pp. 4126-4132 ◽  
Author(s):  
Marike du Plessis ◽  
Vincent J. Smith ◽  
Leonard J. Barbour
Keyword(s):  
Phase Transformation ◽  
Solid State ◽  
Single Crystal ◽  
Phase Transformations ◽  
Guest Molecules ◽  
Solvent Molecules

The acetonitrile guest molecules in this porous metallocycle can be exchanged for different solvent molecules in a single-crystal to single-crystal manner. These guest exchanges are accompanied by a phase transformation in the solid state.

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